The invention relates to a method for treating stock formed of recycled fibre, the method comprising: treating the stock in screen means and a flotation cell means, and screening the stock into accept and reject.
Further, the invention relates to an arrangement for treating stock formed of recycled fibre, the arrangement comprising: a screen member preceding flotation, comprising means for screening the stock into accept of the preceding screening and reject of the preceding screening, which screen member preceding the flotation further comprises a discharge channel for the accept of the preceding screening and a discharge channel for the reject of the preceding screening; a flotation cell means with a feed channel for receiving the accept of the preceding screening as well as a discharge channel for the flotation accept and a discharge channel for the flotation reject; a fine screen member connected to said discharge channel for the flotation accept, which fine screen member comprises means for dividing the flotation accept into fine screen accept and fine screen reject and which fine screen member further comprises a discharge channel for the fine screen accept and a discharge channel for the fine screen reject.
Fibre stock made of recycled fibre, such as wastepaper, hereinafter referred to as ‘stock’, must be screened during the deinking process so that the stickies and dirt specks in the pulp will not disturb further treatment of the stock, for instance formation of a paper web.
It is known to take the pulp fraction removed along with the screen reject to waste disposal, i.e. either to incineration or to a dumping area.
A problem with the above arrangement is that said removed pulp fraction contains not only undesired material but also a large amount of good fibre which could be exploited. According to the present practice, this good fibre is wasted.